A person’s location can be hugely revealing. Here are some tips on how to mask the information your computer and phone transmit automatically.

In the course of writing my book, Dragnet Nation, I tried various strategies to protect my privacy. In this series of book excerpts and adaptations, I distill the lessons from my privacy experiments into tips for readers. – Julia Angwin.

“Where R U?” There’s a reason that is among the most common text messages of the modern age.

Location is one of the most revealing pieces of information about us. In 2013, researchers found that four instances of a person’s location at a given point in time were enough to uniquely identify 95 percent of the individuals they examined. “Human mobility traces are highly unique,” the researchers wrote. “Mobility data is among the most sensitive data currently being collected.”

Location is also predictive. In another study, researchers at Microsoft were able to use location data to predict where people would be in the future. Wednesdays were the easiest to predict, and weekends the hardest. “While your location in the distant future is in general highly independent of your recent location,” the researchers wrote, “it is likely to be a good predictor of your location exactly one week from now.”

To mask my location I took several steps:

1) When browsing the Web, I tried to use the Tor Browser as often as possible. Tor anonymizes the location 2014 known as the IP Address 2014 that you computer transmits automatically to every website you visit. It’s amazing to see how revealing your IP address can be 2014 this site pinpoints my location exactly.

Tor bounces your Internet traffic around the world so that your computer’s location is masked. However, because your traffic is bouncing around the world, using Tor can slow down your Web browsing. Click the Tor button on this graphic to see how Tor protects your location from potential eavesdroppers.

2) Masking my location when using my cellphone was more difficult. I turned off ‘location services’ for my apps. And I tried to opt out from companies that track cellphone users via the Wi-Fi signal emitted by their phone.

I identified 58 companies that appeared to be in the mobile location tracking business 2014 ranging from advertisers to wireless carriers. Of those, only 11 offered opt-outs 2014 which I attempted to complete. Here is the chart of the folks I found that offered opt outs.

The Future of Privacy Forum has also built a location opt-out site, which as of today, offers opt-outs from 11 location tracking companies.

Ultimately, I decided that turning off my Wi-Fi signal was a more effective opt-out.

3) When I really do not want my location to be tracked, I throw my phone into a Faraday cage 2014 a bag that blocks it from transmitting signals to Wi-Fi or the cellphone tower. I use this one from OffPocket, but any Faraday cage will do.

Of course, this also means that I can’t use my phone. So, like most of my privacy fixes, it is a highly imperfect solution.